// header to define some math constants

const double PI = 3.14159265358979323846264338328;

//#ifndef M_PI
//#define M_PI       3.14159265358979323846264338328      /* pi */
//#endif

//#ifndef M_PI_2
//#define M_PI_2     1.57079632679489661923132169164      /* pi/2 */
//#endif